Open mesh woven fibrous absorbent media



Jan. 27, 1970 1 A, MORTENSEN ET AL 3,491,802

OPEN MESH WOVEN FIBRoUs ABSORBENT MEDIA 3 Sheets-Sheet l Filed Jan. l0,196'? Jan. 27, 1970 J. A. MoRTr-:Nsl-:N `ETAI- .OPEN MESH WOVEN FIBROUSABSORBENT MDI.

Filed Jan. l0, 1967 r'llzi- :10o/corded l Qbaze 5 Sheets-Sheet 2 Q0 QQOO g 8o Q OO o ATTORNEY Jan. 27., 1970 J. A. MoRTENsEN ETAI- 3,491,802

OPEN MESH WOVEN FIBROUS ABSORBENT MEDIA 3 Sheets-Sheet 5 Filed Jan. l0,196'? United States Patent O U.S. Cl. 139-420 1 Claim ABSTRACT OF THEDISCLOSURE Multi-ply open mesh Woven absorbent fibrous pads are preparedby (1) weaving an open mesh fabric of yarns consisting mostly ofabsorbent7 preferably nonshrinkable, fibers but also containing highlyshrinkable fibers, (2) subsequently causing the shrinkable fibers toshrink to popcorn the yarns while controlling the shrinking to providewebs having a finished thread count of between and 45 threads per squareinch, and (3) folding the webs thus produced to form the pad. The padsprovided have a higher absorbent capacity and a lower tendency to abradethe surface which they are used to Wipe than do prior art multi-plypads.

BACKGROUND OF THE INVENTION Open mesh woven absorbent fibrous webs suchas gauze and the like have long been folded to form multiply pads andused as wipes for many purposes from the washing of vehicles and thelike on one hand to surgical uses such as the wiping of blood and othersubstances from the skin of a patient on the other. As indicated above,these pads most often consist of a multiplicity of plies of cotton gauzewoven at a thread count of about by 12 threads per inch.

While these gauze wipes have been more than adequate for most purposesto which they have been applied, all concerned have naturally beencontinually searching for materials to form such pads which are improvedin one or more properties. If one were to choose one or two propertiesof gauze wipes which could possibly be improved upon, one would probablychoose to increase the absorbent capacity of the wipe and to lower itstendency to abrade surfaces which it is used to wipe.

SUMMARY OF THE INVENTION According to this invention, an absorbent wipeis provided which is dramatically improved from the standpoint ofpossessing a higher total capacity to absorb fluids and a lower tendencyto abrade the surface which it is used to wipe. Specifically the openmesh, woven, fibrous absorbent wipes of this invention comprise amultiplicity of plies of a woven, open mesh absorbent fabricsuperimposed one on top of the other, said fabric having a yarn count offrom about 15 to about 45 yarns per square inch, most of said yarnsconsisting mostly of absorbent fibers and a majority of said yarnshaving a relatively thin and hard core of generally axially extendingfiber portions surrounded by a relatively thick highly absorbent fluffyand hairy yarn sheath consisting of portions projecting outward from thecore a substantial distance, said projecting fibers in said yarn sheathsin each ply projecting into adjacent plies of the fabric and cooperatingto form a series of three dimensional absorbent and cushioning cellswithin said pad and said sheaths of said yarns adjacent the outersurface of the pad acting to cushion forces applied to the pad duringuse.

In the preferred practice of the invention, the fabric should have athread count of between about 18 and about threads per square inch, ithaving been found that the 3,491,802 Patented Jan. 27, 1970 iceabsorbent capacity of the web is highest when the thread count is withinthis range.

In making the wipes of this invention, a gauze-like material is suitablywoven from yarns consisting of from about 70 to 90% absorbent cellulosicfibers or filaments such as cotton or rayon, which shrinks at mostslightly on heating, and of from.. about l0 to 30% of highly shrinkablefilaments preferably thermoplastic filaments such as polypropylene andthe like which shrink substantially on heating. By then shrinking thehighly shrinkable filaments in the yarns, these filaments are caused toform a small hard yarn core and portions of the cellulosic fibers arecaused to project outward from the core and to thus form the cushioningsheaths and the absorbent cells referred to above. The yarns are bestdescribed as having been popcorned The preferred process utilized inmaking the pads of this invention and the product itself should not beconfused with so-called bulked fabrics of the type described in U.S.Patent 2,627,644 to Foster wherein a gauze-like structure is formed ofnonthermoplastic yarns alternating with thermoplastic yarns and thelatter thereafter shrunken. By thus shrinking the thermoplastic yarns,the nonthermoplastic yarns which do not shrink are caused to buckle andthus the fabric is said to be bulked. However, in webs of that type theindividual nonthermoplastic yarns do not increase substantially in sizeand bulk. The fabric is bulky primarily due to certain yarns as a unitlying out of the general plane of the fabric. In the fabrics of thisinvention, differential shrinkage occurs within the interior of theyarns to give substantial bulk to the yarns themselves.

The preferred process utilized in making the pads of this invention andthe products resulting therefrom should also not be confused withmulti-ply pads formed of fabrics of the type described generally, forexample, in U.S. Patent 3,190,289 to Patience and the process used tomake the same. Fabrics of that type are usually Woven in theconventional manner from cellulosic yarns and immersed in a hot causticbath which is strongly agitated to cause the yarns to assume sinuous ortorturous formations to cause the fabric to shrink and thus become thickand bulky. There is little or no differential shrinkage within a givenyarn and thus the yarns do not have thin hard cores surrounded by thicksoft sheaths of fiber portions projecting outward from the core of theyarn, rather the fabric is bulky primarily because certain yarns projectas a unit out of the general plane of the fabric.

Finally, the multi-ply pads of this invention should not be confusedwith single ply popcorned fabrics in general of the type described inHercules Powder Co. Bulletin FD-3A of May 1, 1963 which describes wovenfabrics made of yarns consisting of cotton, viscose rayon and/or wooland 20% polypropylene filaments, the yarns having been heat shrunken.The products of this invention and the novel and surprising propertiesof the same are dependent on the pad having a finished thread count ofbetween about 15 and about 45 threads per square inch and on the sameand being formed of a plurality of plies of the popcorned fabric.

The invention will be more clearly understood after reading thefollowing description in reference to the appended drawings. In thedrawings,

FIG. 1 is a view in perspective of a conventional prior art gauze wipe;

FIG. 2 is a cross section of the wipe of FIG. 1 taken taken along lines2-2;

FIG. 3 is a plan view of a popcorned absorbent product of thisinvention;

FIG. 4 is a cross section of the product of FIG. 1 taken along lines4-4;

FIG. 5 is a greatly enlarged view in perspective of one absorbent cellwithin the product of FIG. 3;

FIG. 6 is a typical graph of absorbent capacity vis. thread count forboth the prior art wipes and the wipes of this invention;

FIG. 7 is a photomicrograph of a plexiglass surface which has been wipedwith a prior art gauze wipe;

FIG. 8 is a photomicrograph of a plexiglass surface which has been wipedwith a product made in accordance with the Patience Patent 3,190,289;

FIG. 9 is a photomicrograph of a plexiglass surface which has been wipedwith the product of this invention.

Referring now to FIGS. 3-5, the absorbent wipe 11, illustrated thereinconsists of four plies of a 20 by 12 yarns to the inch woven gauze-likeweb 12 superimposed one on another. The individual yarns 13 and 14consist of about 80% ll/zdenier cotton staple having an average lengthof 1% inches and about 20% polypropylene laments having a denier ofabout 3 and an average fiber length of about 1% inches.

The web 12 has been exposed to temperatures of about 325 F. which almostinstantaneously causes the polypropylene filaments in the yarns 13 and14 to shrink by about 50% in both the warp and the fill direction. Thisshrinkage of the polypropylene filaments causes these filaments toconcentrate in the center of the yarn and form a thin hard core 15, asshown in FIG. 5 of the drawings, thus forcing the cotton fibers 16 tomove outward and form a thick soft sheath around the yarn coreconsisting of cotton fiber portions 17 projecting outward from the core.As can be seen most clearly in FIG. 5, the projecting fiber portions 17in adjacent layers 18 and 19 of the pad project from one fabric layerinto adjacent layers and cooperate to form absorbent cells 20 within thepad.

ABSORBENT CAPACITY The parameters used to evaluate and compare theabsorbent capacity of multi-ply wipes is (1) the maximum fluid capacityfor a given area of unfolded fabric and (2) fluid capacity of wipes ofequal fabric weight` The absorbent capacity of the pad 11 illustrated inFIGS. 3-5 is substantially `greater than the absorbent capacity of a padof equal unfolded surface area made of multiple plies of gauze ormultiple plies of material made in accordance with U.S. Patent3,190,289. This is true at all thread counts within the earlierdescribed limits.

In Table I, data is provided comparing the absorbent capacity of thewipes of this invention and conventional gauze wipes made of equalunfolded surface areas (192 square inches) of material. Sample A is the4 inch by 4 inch pad 1, made of 12 plies of 20 by 12 thread to the inchcotton gauze 2, the individual threads 3 and 4 having a cotton count of30s singles in the warp and 40s single in the fill and the fibers in theyarns having a fiber length of about 1%@ inches.

Samples B, C and D are prepared in accordance with this invention. Thefabric is woven from yarns having a cotton count of 30s singles andconsisting of 80% 11/2 denier cotton fibers and 20% 3 denierpolypropylene filaments. The yarns are woven into a fabric at a threadcount of 12 by 7 threads to the inch and the fabric is then passedthrough an oven at 325 F. at low tension in both directions to shrinkthe polypropylene filaments by about 35% and to thus cause thepolypropylene filaments to core and the cotton fibers to project outwardfrom the core. The finished thread count of the fabric is about 20 by 12threads to the inch. Sample B is a six ply 4 inch by 8 inch pad madefrom this fabric while Sample C is a four ply 4 inch by 12 inch pad andSample D is a two ply 4 inch by 24 inch pad. Thus, both the ganze sampleand the popcorned pads have an unfolded surface area of 192 squareinches.

These pads are then subjected to a test for maximum absorbency which iscarried out according to the U.S.P. test for absorbency for cotton andgauze.

TABLE I Sample: Absorbent capacity (gms.)

A 14.65 B 33.40 C 37.80 D 35.60

As can be seen from Table I, the wipes of this invention have anabsorbent capacity of up to 2.5 times that of conventional gauze wipes.

These tests are repeated to compare the performance of wipes of thisinvention with wipes made in accordance with U.S. Patent 3,190,289.Sample E is a l2 ply, 4 inch by 4 inch pad made of a fabric treated asdescribed in U.S. Patent 3,190,289 at a finished thread count of 14 byl0 threads to the inch. Sample F is made in accordance with thisinvention and is a six ply 4 inch by 8 inch pad made of material havingan approximate thread count of 14 by 10 threadsv to the inch. Theresults of these tests are noted in Table II and it can be seen that thewipes of this invention have an absorbent capacity of over two timesthat of wipes of the type described in U.S. Patent 3,190,289.

TABLE II Sample: Absorbent capacity (gms.)

Similar results are obtained when the absorbent capacity of equalweights of each of the pads are compared. These results are tabulated inTables III and IV. Tables III and IV are prepared in the followingmanner:

The 12 ply, 4 by 4 pad of 20 by l2 threads to the inch (Sample A) gauzehas an original weight of 2.35 gms. The other pads formed have a weightsomewhat less than this. Thus, the absorbent capacity data previouslyreported for these other pads is converted to a base weight of 2.35 gms.in order to arrive at the figures in Tables III and IV.

TABLE III Sample: Weight of water absorbed (gms.)

TABLE IV Sample: Weight of water absorbed (gms.)

The reasons for this dramatic increase in the absorbent capacityprovided by this invention can again best be seen by reference to FIG.5. As the polypropylene filaments 15 in the yarns shrink and core thuscausing the cotton yarns 16 to bulk substantially and project generallyoutward from the core. Thus, when several layers of the fabric are pliedtogether, the projecting fiber portions 17 in the adjacent layers 18 and19 tend to cooperate to form the three dimensional absorbent cells 20referred to earlier. In addition, each individual yarn itself is moreabsorbent due to its more open fluffy outer portion or sheath thusforming highly absorbent areas 21 around the absorbent cells 20. Ofcourse, the web interstices in adjacent layers will not usually be inregistry as shown in FIG. 5 and the absorbent cells may be torturous inshape, however, FIG. 5 is meant to illustrate the principle involved.

As can be seen from the typical graph of FIG. 6, comparing the absorbentcapacity of multi-ply gauze pads and multi-ply pads of this invention onan equal weight basis,

the pads of this invention have a substantially greater absorbentcapacity than do the prior art pads for any web having a thread countbetween 15 and 45 threads per square inch. This includes finished webconstructions having a thread count as low as by 8 as well as threadcount as high as 24 by 20. However, it is expected that in the practiceof the invention, webs having a thread count of between about and about35 threads per inch will be utilized since it has been found that thecurve of absorbent capacity vs. thread count reaches a maximum at athread count of about threads per square inch.

WET RESILIENCE The absorbent -pads also have a substantially higher Wetresilience than do prior art gauze pads or any of the other prior artpads heretofore referred to. Wet resilience is determined by placing a300 gm. weight on top of a pad which is saturated with fluid. The weightis removed and after one hour the thickness of the pad is compared tothe thickness of the pad prior to the placing of the weight on the same.Typical 12 iply, 20 by 12, gauze pads have a wet resilience of aboutll/2%. However, 6 ply, 20 by 12, pads of this invention have a wetresilience of over 38%. This property is important to the pad retainingits bulk when wet and thus retaining its high absorbency. The high wetresilience is thought to be due to the cushioning effect caused by thecooperation of the soft hairy outer yarn portions of yarns in adjacentlayers of the pad.

TENDENCY TO ABRADE As previously mentioned, it has also beensurprisingly found that the pads of this invention have a substantiallylower tendency to abrade the surface which they are used to wipe than doconventional gauze wipes or wipes prepared in accordance with U.S.Patent 3,190,289 to Patience. Despite this low tendency to abrade, it isfound that the wipes of this invention in fact tend to have a betterdegree of scrubability than the prior art wipes because of the improvedwet resilience referred to above. In a controlled test, a Plexiglassairplane windshield was wiped with three different absorbent wipes. Thepane of plexiglass was wiped with a conventional gauze wipe of the typepreviously described. It was found that grooves of considerable depthwere formed in the same, which illustrates that prior art gauze wipesmay tend to seriously and permanently abrade certain surfaces which theyare used to Wipe. In gauze wipes, a hard and rigid yarn contacts thesurface being wiped. As one presses very hard on the wipe, yarns inoutward lying gauze layers also contact the surface through the windowsor openings in the surface layer.

In a second wipe of a pane of Plexiglass the wipe prepared in accordancewith U.S. Patent 3,190,289 to Patience was employed. While the groovesformed on this pane of plexiglass are not quite as deep as those on thepane of Plexiglass wiped with the conventional gauze wipe, they are muchgreater in number. The yarn portions contacting the Plexiglass are stillhard and rigid and since the threads follow a torturous path, many morecontact the Plexiglass surface when pressure is applied to the pad.

In a third wipe of a pane of Plexiglass the wipes prepared in accordancewith this invention were employed. After wiping has been completed,essentially no permanent or deep grooves are found in the Plexiglass.The cushioning effect of the cooperating soft hairy outer yarn portionsin adjacent layers within the absorbent pad tend to absorb somewhat theforces exerted downward on the pad by the user and to distribute theseforces more evenly along the surface of the pad touching the surfacewhich is to be wiped. In addition, instead of harsh hard yarn portionstouching the surface which is wiped, the surface is contacted by thesoft outer yarn portions of both the yarns at the surface of the pad andthe yarns in inner layers of the pad which contact the surface beingwiped through the interstices in the outer layers of the pad.

The successful popcorning of the fabric and therefore the successfulcreation of the three dimensional and cushioning cells previouslyreferred to and described is dependent on `a number of parametersincluding, for example, the length of the staple fibers in the yarns,the denier of the fibers in the yarns, the yarn size itself, the twistand twist multiplier of the yarns, the percentage of thermoplasticfibers in the yarns, and the degree of shrinkage to which thethermoplastic fibers are subjected.

The thermoplastic fibers may be present in the yarns in amounts ofbetween about 5 and about 35%. As the lower level of these limits isreached, the yarns usually lack sufficient pullback power to causesufficient popcorning of the yarns in most fabric constructions.However, above about 35% the yarns seem to lack sufiicient bulk in thefinal product. This is probably due to the high proportion ofthermoplastic fibers causing the yarns to be rather hard and stiff anddue to the lack of a sufiicient number of fibers projecting outward fromthe core of the yarns.

The denier of the thermoplastic fibers may be varied between about 1.5and about 6, however, when deniers much above 6 are utilized, there maybe a high degree of fiber slippage during the heat shrinking process andthus adequate popcorning of the yarns may not be obtained. In selectingthe staple length of the polypropylene fiber, lengths of above about 1inch may be used. However, very long staples will tend to reduce thecoring effect previously described while very short staples will tend toincrease the possibility of fiber slippage during the heat treatment,thus substantially reducing the bulk. Preferably polypropylene fibershaving a staple length of somewhere between about 1 and 11/2 inchesshould be utilized.

Two of the most important parameters in successfully providing productsaccording to this invention are the twist multiplier of the yarns andthe degree of shrinkage. If the twist multiplier of the yarns is muchabove about 4.75, popcorning will not occur and the same will remainhard as in the prior art fabrics. However, if the twist multiplier ismuch below about 3, it is difficult to handle the yarns and form theweb. In order to provide the effects noted earlier, the yarns must beshrunken suiciently to cause coring and to cause the absorbent fibers toproject well outward from the core. It has been found that this can beaccomplished by shrinking the yarns anywhere from about 15% to about65%. However, in the preferred practice of the invention, shrinkage ofabout 25% to 50% will be utilized.

It has been found that the improvements disclosed herein may be obtainedwhile utilizing any of the cellulosic fibers as the nonthermoplasticcomponent of the yarn, although cotton or rayon fibers are preferred.While it is desirable that each yarn have the popcorned constructionillustrated and described, imperfections in the bulking process makethis generally impossible and up to about half of the yarns or up toabout half of the length of any given yarn may not be popcorned at all.It may be desirable in some cases to construct the fabrics onlypartially of yarns which can be popcorned In the samples used for thetest results, tabulated in Tables I to V, a close examination shows thatonly about 1/2 of the yarns or yarn lengths were bulked.

While specific examples of products of this invention have beendescribed, they are meant to be only illustrative of the broaderinventive concept, which is limited only by the claims. For example,while differential heat shrinking has been disclosed as a specificmethod of providing popcorned yarns, other shrinking methods, such as,differential moisture shrinking may be used. In addition, shrinking neednot be used at all, the finished yarn constructions described beingprovided by other methods.

What is claimed is:

1. A Woven open mesh absorbent pad comprising a multiplicity of plies ofa woven open mesh absorbent fabric superimposed one on top of the other,said fabric having a yarn count of from about 15 to about 45 yarns persquare inch, most of said yarns consisting mostly of absorbent bers anda majority of said yarns having a relatively thin and hard core ofgenerally axially extending thermoplastic fiber portions surrounded by arelatively thick absorbent fluffy and hairy yarn sheath consisting ofcellulosic ber portions projecting outward from the core a substantialdistance, said projecting bers of said yarn sheaths in each plyprojecting into adjacent plies of the fabric and cooperating to form aseries of three dimensional absorbent and cushioning cells within saidpad and said yarn sheaths adjacent the surface of the pad acting tocushion forces applied to the pad during use.

References Cited UNITED STATES PATENTS 2,656,585 10/1953 Jackson.3,190,289 6/1965 Patience 12S- 296 3,367,333 2/1968 Scheier 12S-284HENRY S. JAUDON, Primary Examiner.

U.S. Cl. X.R. 128-296

